base/memory/ref_counted_memory.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_MEMORY_REF_COUNTED_MEMORY_H_
   6 #define BASE_MEMORY_REF_COUNTED_MEMORY_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/base_export.h"
  12 #include "base/compiler_specific.h"
  13 #include "base/memory/ref_counted.h"
  14
  15 namespace base {
  16
  17 // A generic interface to memory. This object is reference counted because one
  18 // of its two subclasses own the data they carry, and we need to have
  19 // heterogeneous containers of these two types of memory.
  20 class BASE_EXPORT RefCountedMemory
  21     : public base::RefCountedThreadSafe<RefCountedMemory> {
  22  public:
  23   // Retrieves a pointer to the beginning of the data we point to. If the data
  24   // is empty, this will return NULL.
  25   virtual const unsigned char* front() const = 0;
  26
  27   // Size of the memory pointed to.
  28   virtual size_t size() const = 0;
  29
  30   // Returns true if |other| is byte for byte equal.
  31   bool Equals(const scoped_refptr<RefCountedMemory>& other) const;
  32
  33  protected:
  34   friend class base::RefCountedThreadSafe<RefCountedMemory>;
  35   RefCountedMemory();
  36   virtual ~RefCountedMemory();
  37 };
  38
  39 // An implementation of RefCountedMemory, where the ref counting does not
  40 // matter.
  41 class BASE_EXPORT RefCountedStaticMemory : public RefCountedMemory {
  42  public:
  43   RefCountedStaticMemory()
  44       : data_(NULL), length_(0) {}
  45   RefCountedStaticMemory(const unsigned char* data, size_t length)
  46       : data_(length ? data : NULL), length_(length) {}
  47
  48   // Overridden from RefCountedMemory:
  49   virtual const unsigned char* front() const OVERRIDE;
  50   virtual size_t size() const OVERRIDE;
  51
  52  private:
  53   virtual ~RefCountedStaticMemory();
  54
  55   const unsigned char* data_;
  56   size_t length_;
  57
  58   DISALLOW_COPY_AND_ASSIGN(RefCountedStaticMemory);
  59 };
  60
  61 // An implementation of RefCountedMemory, where we own our the data in a
  62 // vector.
  63 class BASE_EXPORT RefCountedBytes : public RefCountedMemory {
  64  public:
  65   RefCountedBytes();
  66
  67   // Constructs a RefCountedBytes object by _copying_ from |initializer|.
  68   explicit RefCountedBytes(const std::vector<unsigned char>& initializer);
  69
  70   // Constructs a RefCountedBytes object by performing a swap. (To non
  71   // destructively build a RefCountedBytes, use the constructor that takes a
  72   // vector.)
  73   static RefCountedBytes* TakeVector(std::vector<unsigned char>* to_destroy);
  74
  75   // Overridden from RefCountedMemory:
  76   virtual const unsigned char* front() const OVERRIDE;
  77   virtual size_t size() const OVERRIDE;
  78
  79   const std::vector<unsigned char>& data() const { return data_; }
  80   std::vector<unsigned char>& data() { return data_; }
  81
  82  private:
  83   virtual ~RefCountedBytes();
  84
  85   std::vector<unsigned char> data_;
  86
  87   DISALLOW_COPY_AND_ASSIGN(RefCountedBytes);
  88 };
  89
  90 // An implementation of RefCountedMemory, where the bytes are stored in an STL
  91 // string. Use this if your data naturally arrives in that format.
  92 class BASE_EXPORT RefCountedString : public RefCountedMemory {
  93  public:
  94   RefCountedString();
  95
  96   // Constructs a RefCountedString object by performing a swap. (To non
  97   // destructively build a RefCountedString, use the default constructor and
  98   // copy into object->data()).
  99   static RefCountedString* TakeString(std::string* to_destroy);
 100
 101   // Overridden from RefCountedMemory:
 102   virtual const unsigned char* front() const OVERRIDE;
 103   virtual size_t size() const OVERRIDE;
 104
 105   const std::string& data() const { return data_; }
 106   std::string& data() { return data_; }
 107
 108  private:
 109   virtual ~RefCountedString();
 110
 111   std::string data_;
 112
 113   DISALLOW_COPY_AND_ASSIGN(RefCountedString);
 114 };
 115
 116 // An implementation of RefCountedMemory that holds a chunk of memory
 117 // previously allocated with malloc or calloc, and that therefore must be freed
 118 // using free().
 119 class BASE_EXPORT RefCountedMallocedMemory : public base::RefCountedMemory {
 120  public:
 121   RefCountedMallocedMemory(void* data, size_t length);
 122
 123   // Overridden from RefCountedMemory:
 124   virtual const unsigned char* front() const OVERRIDE;
 125   virtual size_t size() const OVERRIDE;
 126
 127  private:
 128   virtual ~RefCountedMallocedMemory();
 129
 130   unsigned char* data_;
 131   size_t length_;
 132
 133   DISALLOW_COPY_AND_ASSIGN(RefCountedMallocedMemory);
 134 };
 135
 136 }  // namespace base
 137
 138 #endif  // BASE_MEMORY_REF_COUNTED_MEMORY_H_